The present invention relates to a process for the carboxylation of olefins by the use of cobalt carbonyl catalyst, and particularly it relates to a process for the carboxylation of olefins which renders it possible to recover the applied cobalt carbonyl catalyst easily in reusable state.
As is generally known, when carbon monoxide together with water or carbon monoxide together with alcohol is made to react with olefins in the presence of cobalt carbonyl catalyst, there can be produced carboxylic acid or ester of carboxylic acid. On this occasion, in order to reuse the cobalt carbonyl compound applied as catalyst, it is natural that the catalyst should be recovered from the reacted mixture arising from said carboxylation reaction. As the means of recovering said catalyst, there are known two methods: one is a method of recovering the catalyst as metal cobalt through decomposition by heating the catalyst contained in the reacted mixture while blowing hydrogen or steam into said mixture, and the other is a method of recovering the catalyst in the form of cobalt salt by adding acid to the reacted mixture.
However, these conventional methods for the recovery of catalyst are all inadvisable inasmuch as they necessitate relatively complicated processes, and the metal cobalt and cobalt salt recovered thereby cannot be directly used as the carboxylation catalyst so that they must be converted into cobalt carbonyl compound for the purpose of reuse thereof.